Although most asteroids are found in the belt of space between Mars and Jupiter, not all of them reside there. Apophis belongs to a group known as the Aten family. These do not belong to the asteroid belt and spend most of their time inside the orbit of the Earth, placing them between our planet and the sun.

That makes them particularly dangerous because they spend the majority of their orbit close to the sun, whose overwhelming glare obscures them to telescopes on Earth – rather like a second world war fighter ace approaching out of the sun.

Having crossed outside Earth's orbit, Apophis will appear briefly in the night-time sky. Wednesday 9 January will afford astronomers the rare opportunity to bring a battery of telescopes to bear: from optical telescopes to radio telescopes to the European Space Agency's Infrared Space Observatory Herschel. Two of the biggest unknowns that remain to be established are the asteroid's mass and the way it is spinning. Both of these affect the asteroid's orbit and without them, precise calculations cannot be made.

Global warming is turning the volume of extreme weather up, Spinal-Tap-style, to 11. The temperature forecast for next Monday by Australia's Bureau of Meteorology is so unprecedented - over 52C - that it has had to add a new colour to the top of its scale, a suitably incandescent purple.

Australia's highest recorded temperature is 50.7C, set in January 1960 in South Australia. The record for the hottest average day across the nation was set on Monday, at 40.3C, exceeding a 40-year-old record. "What makes this event quite exceptional is how widespread and intense it's been," said Aaron Coutts-Smith, the weather bureau's climate services manager. "We have been breaking records across all states and territories in Australia over the course of the event so far." Wildfires are raging across New South Wales and Tasmania.